##### http://autoconf-archive.cryp.to/ac_check_typedef.html
#
# SYNOPSIS
#
#   AC_CHECK_TYPEDEF(TYPEDEF, HEADER [, ACTION-IF-FOUND [, ACTION-IF-NOT-FOUND ]])
#
# DESCRIPTION
#
#   Check if the given typedef-name is recognized as a type. The trick
#   is to use a sizeof(TYPEDEF) and see if the compiler is happy with
#   that.
#
#   This can be thought of as a mixture of
#   AC_CHECK_TYPE(TYPEDEF,DEFAULT) and
#   AC_CHECK_LIB(LIBRARY,FUNCTION,ACTION-IF-FOUND,ACTION-IF-NOT-FOUND).
#
#   A convenience macro AC_CHECK_TYPEDEF_ is provided that will not
#   emit any message to the user - it just executes one of the actions.
#
# LAST MODIFICATION
#
#   2006-10-30
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of the
#   License, or (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful, but
#   WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
#   As a special exception, the respective Autoconf Macro's copyright
#   owner gives unlimited permission to copy, distribute and modify the
#   configure scripts that are the output of Autoconf when processing
#   the Macro. You need not follow the terms of the GNU General Public
#   License when using or distributing such scripts, even though
#   portions of the text of the Macro appear in them. The GNU General
#   Public License (GPL) does govern all other use of the material that
#   constitutes the Autoconf Macro.
#
#   This special exception to the GPL applies to versions of the
#   Autoconf Macro released by the Autoconf Macro Archive. When you
#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([AC_CHECK_TYPEDEF_],
[dnl
ac_lib_var=`echo $1['_']$2 | sed 'y%./+-%__p_%'`
AC_CACHE_VAL(ac_cv_lib_$ac_lib_var,
[ eval "ac_cv_type_$ac_lib_var='not-found'"
  ac_cv_check_typedef_header=`echo ifelse([$2], , stddef.h, $2)`
  AC_TRY_COMPILE( [#include <$ac_cv_check_typedef_header>],
	[int x = sizeof($1); x = x;],
        eval "ac_cv_type_$ac_lib_var=yes" ,
        eval "ac_cv_type_$ac_lib_var=no" )
  if test `eval echo '$ac_cv_type_'$ac_lib_var` = "no" ; then
     ifelse([$4], , :, $4)
  else
     ifelse([$3], , :, $3)
  fi
])])

dnl AC_CHECK_TYPEDEF(TYPEDEF, HEADER [, ACTION-IF-FOUND,
dnl    [, ACTION-IF-NOT-FOUND ]])
AC_DEFUN([AC_CHECK_TYPEDEF],
[dnl
 AC_MSG_CHECKING([for $1 in $2])
 AC_CHECK_TYPEDEF_($1,$2,AC_MSG_RESULT(yes),AC_MSG_RESULT(no))dnl
])
